I hear your frustration. As you say, this is an unusual number of flats. Have you done a thorough check of the inside of the tire to make sure that there are no sharpies in there? I'd also check the rim and, even though you have rim tape, check that too. If all checks out, maybe you need different tubes? I ride a 29er most of the time with 700x35 tires at 70psi so I am not stressing either the tube or tire, your tire pressure may require a higher quality tube or one made from a different material than what you are currently using.